1. Field of the Invention
The present invention relates to an optical recording apparatus to form a preformat onto an optical disc.
2. Description of the Background
It is proposed to provide an optical disc on which the Table of Contents (TOC) information, a pulse signal of a predetermined period, and the like are prerecorded as pits or bumps on the lead-in track or lead-out track as well as a wide groove, for recording data signal therein provided. FIG. 1, shows the region in which pits 31 are preformed and a wide groove 32 mixedly exist on a recordable optical disc. Hitherto, in the case of forming patterns of different widths onto a mother disc, the pits 31, groove 32, and recording spots corresponding to their widths are prepared and both of these recording spots are switched.
In the case of independently forming pits 31 and grooves 32 having different widths by a different recording spots, the following problems occur.
First, in the case of changing the spot sizes by changing the effective numerical aperture (NA) by using the same lens, the ratio of the sizes of the spots cannot be set to a large value. For example, both having a spot of the width of 0.5 [.mu.m] and the groove of the width of 1.1 [.mu.m] cannot be formed.
Second, since it is necessary to form two beams, the laser power must to be set to a large value.
Third, in the case of the spot of a large diameter, if its shape is not well shaped, a groove would not be formed with sharp cross sectional configuration.
Fourth, the groove width is easily changed due the exposure level and developing condition.